Master's Theses

Document Type

Thesis - campus only access

Date of Award

Spring 2008

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Eric Gillock

Abstract

Changing environmental conditions and increased water consumption has transformed many historically perennial stream systems into intermittent systems. Multiple drying and wetting events throughout the year might impact many stream processes. Two such processes, nitrification and denitrification, are also key components of the nitrogen (N) cycle. They function to first, through nitrification convert ammonium (NH4+) to nitrate (NO3-). Then second, through denitrification convert NO3- to dinitrogen gas (N2) thus effectively removing N from the system. During the summer 2007, an experimental stream constructed adjacent to the Saline River in Western Kansas was used to determine the effects of desiccation and rewetting of stream sediment on nitrification and denitrification potentials. Mean nitrification and denitrification rates in sediment not dried (controls) were 0.431 ± 0.017 ¼g NO3- -N cm-2 h-1 and 0.926 ± 0.106 ¼g N2O-N cm-2 h-1, respectively. As sediment samples dried, nitrifications rates decreased. Sediments dried less than seven days recovered within one day of being rewetted, and sediments dried 21 days recovered by the third day of inundation. Denitrification rates were not affected by one day of drying, but sample dried greater than one day experienced reduced rates of denitrification. Denitrification in sediments dried seven days or less and 21 days recovered by day seven of being rewetted. Rates in sediments dried 14 and 28 days did not fully recover, for either process, even after 28 days of being rewetted. These results demonstrate that alternations in stream’s hydrology can significantly affect nitrogen cycle processes.

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Rights

© 2008 Bradley J. Austin

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